VG in exculsive mode

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VG in exculsive mode

Can i know the difference for exclusive mode and shared mode in a VG.

How to check this in VG
Acclaimed Contributor

Re: VG in exculsive mode

"vgdisplay" will show you.

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Johnson Punniyalingam
Honored Contributor

Re: VG in exculsive mode

# vgchange -a e vgname
Activated volume group in Exclusive Mode.

above command will activate the (Volume Group) in exclusive mode, (man vgchange)

check with "vgdisplay"

from below vgdisplay /dev/vgname output check "VG Wrire Access" - shows "exculsive"

--- Volume groups ---
VG Name /dev/vg01
VG Write Access exculsive -->
VG Status available

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Honored Contributor

Re: VG in exculsive mode

These modes are only applicable to package VGs in Serviceguard clusters, i.e. VGs that have the cluster mode enabled (vgchange -c y ).

Exclusive mode = only one node at a time may activate the VG. This is the default mode for cluster VGs.

Shared mode = more than one node may have the VG active simultaneously. This is used only with special software configurations that can access the VG safely, for example with VGs containing raw data LVs for Oracle RAC high-availability database. The Serviceguard packages containing VGs like this will be configured as special multi-node packages.

A VG cannot be extended or otherwise modified while it is in shared mode. To modify such a VG, you must temporarily switch it back to exclusive mode. To do that, you must deactivate the shared VG on all nodes except one. Then you can use "vgchange -a e " to switch the VG to exclusive mode, then perform the necessary VG modifications. After that, return the VG to shared mode with "vgchange -a s ", and restart the software on the other nodes.

If you have, for example, a three-node Oracle RAC database cluster, this means your cluster DB performance will be reduced while you do the VG modifications, as only 1 node out of 3 can service your database clients at the time. But the database can still be "up" while you do the modifications.

Kapil Jha
Honored Contributor

Re: VG in exculsive mode

beautifully explained above :)
in short.
exclusive=can only be active on one node at one point of time, and it can be active on more than one machine.

shared=can be active on various machines at one point of time.Application would decide if this would currupt the FS or not.

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Honored Contributor

Re: VG in exculsive mode


#vgdisplay vgxx |grep "VG Status"

Exclusive mode:

VG Status available, exclusive

Shared mode:

VG Status available

# man vgchange